Steam collection system for dishwashing machines

ABSTRACT

A system for collecting and condensing steam from dishwashers to recover the heat of condensation and to reduce the humidity in the dishwashing room. Steam is drawn from the dishwasher by a blower into a duct, and through a body of porous material against which sprays of water are directed. Condensed moisture is collected by a baffled sump and returned to a supply of rinse water, or otherwise utilized to recover the heat of condensation of the steam. The airflow leaving the blower is discharged into the room at a reduced level of humidity.

United States Patent [72] Inventor Clyde R. wen, Jr.

Needlmm K 81 Mm. [211 Appl. No. 849,381 [22] Filed Aug. 12, 1969 [45] Patented Aug. 10, 1971 [73] Asaignee Adamation inc.

Newton, Mas.

[54] STEAM COLLECTION SYSTEM FOR DISHWASHING MACHINES 13 Claims, 3 Drawing 13 [52] U.S.Cl. 134/107, 134/70, 134/109 [51] Int. Cl. ..B08b 15/02, 1308b 3/02 [50] Field ofSeareli 134/70, 105, 107, 108, 109

[56] References Cited UNIT ED STATES PATENTS 1,624,026 4/1927 Utz 134/105 UX 2,390,757 12/1945 Voris 134/105 UX 3,308,839 3/1967 Barday 134/109 X 3,435,835 4/1969 Hobbs 134/108 FORElGN PATENTS 738,312 8/1943 Germany 134/107 Primary Examiner-Robert L. Bleutge Attorney-Rich & Ericson ABSTRACT: A system for collecting and condensing steam from dishwashers to recover the heat of condensation and to reduce the humidity in the dishwashing room. Steam is drawn from the dishwasher by a blower into a duct, and through a body of porous material against which sprays of water are directed. Condensed moisture is collected by a baffled sump and returned to a supply of rinse water, or otherwise utilized to recover the heat of condensation of the steam. The airflow leaving the blower is discharged into the room at a reduced level of humidity.

I i l;

STEAM COLLECTION SYSTEM FOR DISHWASHING MACHINES BACKGROUND AND BRIEF DESCRIPTION Commercial dishwashing machines are usually fitted with external duct systems designed to carry away the steam which is emitted by the circulation of turbulent hot water within the machines. These duct systems consist of various shapes of hoods and piping which lead from the dishwashing machine to the exterior of the building and are generally fitted with a fan to create the draft necessary to force the steam out of the building. It is common for the steam to condense in the duct prior to leaving the building, and it is therefore necessary to have the duct work watertight, and to have drain connections fitted to the low places in the system. It is not uncommon to find steam escaping from the machine or leaks in the duct work, which causes damage to ceilings and also creates very uncomfortable working conditions. Such duct systems are expensive, and also require considerable space. They also waste the heat of the steam, discharging it into the atmosphere. But simply to allow the steam to escape directly into the scullery or kitchen would create unbearable working conditions.

It is an object of this invention to improve the working atmosphere in rooms containing dishwashing machines, and at the same time to recover heat otherwise wasted in the discharge of steam from these machines. It is a further object to eliminate the need for installing expensive exterior-opening duct systems with commercial dishwashing machines. It is another object to utilize the heat of the waste steam, as for example to preheat water used in a rinsing or prewashing phase of the dishwashing cycle. Other objects and advantages of the invention will become apparent as the following description proceeds.

Briefly stated, according to a preferred embodiment of the invention, 1 mount a short vertical duct above a hot water rinse compartment of a conventional dishwashing machine, and connect the inlet of the duct to receive a flow of air and steam from the rinse compartment. A blower mounted in the duct passes this gas flow through one or more bodies of porous material, which fill the cross-sectional area of the duct, and may be formed of expanded polyurethane foam coated with polyvinyl chloride, or other insoluble nontoxic foam materials. An arrangement of nozzles sprays streams of water, at ordinary tapwater temperature, onto at least one surface of one of the bodies of foam. To obtain a maximum area of surface contact between the spray and the steam, the spray is directed downwardly against the upper surface of the foam body, in opposite direction to the upward flow of the steam. A further body of foam may be placed in the duct above the first, to provide a site for condensation of any vapor remaining in the airstream leaving the lower body. The airstream is then discharged directly into the dishwashing room, and exhibits a greatly diminished humidity.

The condensed moisture accumulated in the porous bodies, together with the spray of tapwater, drains downwardly to the bottom of the condensing duct. This water is prevented from reentering the rinse compartment by a baffle, and is collected in a sump. It is heated by the heat of condensation of the steam, and l preferably pass it into a tank of water used for prerinsing the dishes, in order to use this recovered heat to good purpose. The heated water may of course be usefully employed in other ways in the kitchen, for example as a medium for grinding ofgarbage.

In a preferred application of the invention, 1 add two such condensing ducts to a conventional commercial dishwashing machine, one for drawing steam from a prewashing compartment at the entrance end of the dishwasher, and the other for cooperation with a final rinse compartment at the exit end of the machine. Depending on the relative temperatures chosen for the streams of rinse water that are sprayed into these compartments, the water collected form the hotter one of the two condensing ducts may be passed to a sump tank which supplies the rinse water for the cooler compartment. The water collected by the other condensing duct from the cooler compartment can be discharged, or reheated and recirculated if that proves more economical.

While the specification concludes with claims particularly pointing out the subject matter which I regard as my invention, it is believed that a clearer understanding may be gained from the following detailed description of a preferred embodiment of the invention, referring to the accompanying drawings, in which:

FIG. 1 is a view in front elevation, and partially in section, of a dishwashing machine incorporating the improved steam collection system;

FIG. 2 is a schematic plan view showing the general arrangement of a conveyor portion of the dishwashing machine; and

FIG. 3 is a sectional view of a portion of the steam collection system, taken along line 3-3 in FIG. 1, looking in the direction of the arrows.

In the drawings, a dishwashing machine of a conventional type, used commercially in restaurants, hotels, and institutions, includes a housing 10 forming a tunnel. The tunnel is subdivided by a series of dependent flexible curtains or partitions 17 into a series of compartments in each of which a different phase of the dishwashing operation is performed. By way of illustration, these are shown as a prerinsing compartment 16, a washing compartment 18, a rinsing compartment 20, and a final rinsing compartment 22. Dishes are carried successively and continuously through these compartments in racks 14, which are connected together and moved around an oval track 12 in a well-known manner. The flexible curtains 17 are pushed aside by the dishes as they pass, but form a sufficient separation of the compartments to allow the various washing steps to be performed at different temperatures.

A series of sump tanks 42, 48, 54 and 60 are arranged below the dishwashing tunnel, one below each compartment l6, 18, 20 and 22, to catch water draining from these compartments. The primary supply of water into the system is furnished through a valve 41 into a spray nozzle 39 in the final rinse compartment, and this water is normally heated to about 180 F. by a conventional water heater (not shown), to sterilize the dishes before they emerge from the tunnel 10 for air-drying. The same supply valve 41 may be used to supply makeup water to the washing and rinsing compartments l8 and 20 as necessary to compensate for water leaving the machine on the dishes and racks, but these connections are not shown to avoid undue complexity of the drawings.

Water draining from the dishes in the final rinse compartment 22 is caught by a tank 60, and is drawn through an outlet 28 by a pump 26 and a conduit 25 to supply a spray nozzle in the prerinsing compartment 16. This compartment serves principally to displace food particles from the dishes, and a water temperature of F. is sufficient for the purpose. The relatively cool and particle-filled water draining from the prerinsing compartment is received in the tank 42 and discharged to a waste line 44 through a valve 46.

The washing compartment 18 has a spray nozzle 30, which receives a water and detergent mixture at about F. from a tank 48, via a conduit 31 having an inlet 34, and under pressure supplied by a pump 32. A heater 50 in the tank 48 maintains the wash water at the proper temperature, and a standpipe 52 opens into the tank to drain off the water as it surpasses a predetermined level. Similarly, the rinsing compartment 20 has a spray nozzle 36, which receives hot water at about F. from a tank 54 via a conduit 37 having an inlet 40, under pressure supplied by a pump 38. A heater 56 in the tank 54 maintains the rinse water at the proper temperature, and a standpipe 58 opens into the tank to drain off the rinse water as it surpasses a predetermined level. The washing machine thus far described is conventional, and in itself forms no part of the present invention.

Mounted on top of the tunnel 10, above the final rinsing compartment 22 and the prerinsing compartment 16, is a pair of vertical ducts or housings 64 and 65, which communicate with these compartments via inlet openings 94 and 95, respectively. As both of the steam collection systems housed by these ducts are identical, one is shown in an exterior view in FIG. 1, and one in cross section.

Steam generated by the sprays of hot water in the compartments 16 and 22 is drawn upwardly both by convection and by blower fans 80 driven by motors 78. Each motor is mounted in a circular cylindrical fan shroud 74, closely surrounding the tips of the fans 80 to increase the efficiency of the blowers. The motors are supported by radial arms 82 in the shrouds 74, which are supported at the upper ends of the ducts 64 and 65 by flanges 77. The blowers discharge through upper open ends 76 of the ducts, directly into the dishwashing room.

Suspended in each duct 64 and 65, on peripheral supports 81 and 83, respectively, are a number of bodies 86 and 84 of porous foam material. 1 have found that expanded polyurethane having a pure vinyl coating, and exhibiting about pores per linear inch, is a highly satisfactory material. This material is commercially available from The Scott Paper Company, Foam Division, Rochester, Pennsylvania. The bodies 86 and 84 have dimensions conforming to and filling the entire cross-sectional areas of the ducts 64 and 65 so that the entire flow of steam must pass through them successively.

A nozzle 88 is arranged above the bodies 86, and is supplied with water at ordinary tap temperature, to spray streams of water downwardly against the upper surface of the uppermost body. The water flows over the extensive interior pore surfaces of the bodies, mixing in intimate surface contact with the rising flow of steam and condensing it rapidly. The heat of condensation raises the temperature of the condensed moisture, which then falls downwardly to the bottom of the duct. The body 84 is placed above the nozzle 88 to trap and condense any evaporated moisture escaping upwardly from the sprayed bodies 86, further reducing the moisture content of the airstream leaving the outlet 76.

The inlet openings 94 and 95 at the bottoms of the ducts 64 and 65 are shielded against the falling streams of condensed moisture by baffles 90, to prevent this water from reentering the tunnel 10. The baffles extend transversely across the ducts and have downwardly sloping edges, as shown in FIG. 3, to drain the moisture into sumps 96, which are separated from the inlet openings 94 and 95 by upstanding partitions 92 surrounding these openings.

The water collected in the sump of the duct 64 associated with the final rinsing compartment 22, being condensed from vapor at about 180 F., is sufficiently hot to be used for the prerinsing operation in the compartment 16. l accordingly drain this water from the sump through a conduit 98 into the tank 60, from which the prewashing water supply is drawn by the pump 26.

The water received in the sump of the duct 65 associated with the prewashing compartment 16 is, on the other hand, condensed from vapor which is originally at only about 120 F., and is not warm enough to be used without reheating. I therefore generally prefer to drain this water through a conduit 100 directly to the waste tank 42, or to use it as a medium for garbage grinding. If desired, however, it may be returned to one of the tanks 48 or 54 for reheating and reuse. The use of the second steam collection duct 65 to condense vapor generated in the prewashing compartment 16 therefore does not have the same purpose of collecting useful heat from condensed steam as does the duct 64 associated with the final rinsing compartment 22. Nevertheless, I prefer to employ both ducts, as otherwise a certain amount of steam or vapor may escape into the room past the curtain 17 closing the inlet end of the dishwashing tunnel. However. it should be understood that the duct 64 may be advantageously used alone, if desired.

The porous surfaces of the bodies 84 and 86 eventually become coated with films of organic or chemical deposits, and it is therefore desirable to clean or replace these bodies at intervals. I provide a door opening 103 in the front of each duct 64 and 65, which receives a sliding door 66 having a handle 68. These doors can be lowered into projecting lips 69 formed in the ducts at the bottoms of the door openings, so that the bodies 84 and 86 can be removed for cleaning or replacement.

What I claim is:

l. A dishwashing machine comprising:

tunnel means forming at least one rinse compartment; first means for spraying hot steam-generating water into said rinse compartment; a collection tank arranged beneath and opening into said rinse compartment to collect water draining therefrom;

a steam collection system comprising a duct connected in gas flow communication with said rinse compartment to receive a flow of gas therefrom, a blower arranged in said duct to draw a flow of gas therethrough, said duct having a discharge outlet arranged to exhaust said flow of gas from said blower, a body of porous material interposed in said duct for passage of said flow of gas therethrough and providing an enlarged surface area for condensation of moisture thereon, second means for spraying water onto said body to aid in condensing moisture thereon, and sump means constructed and arranged for collecting condensed moisture draining from said body, said sump means being connected to discharge collected moisture into said rinse compartment.

2. A dishwashing machine as recited in claim I, said tunnel means being subdivided to form a further rinse compartment, together with third means for spraying water into said further rinse compartment, said third spraying means being connected to draw a supply of water from said collection tank associated with said first-mentioned rinse compartment.

3. A dishwashing machine as recited in claim 2, together with a further steam collection system comprising a further duct connected in gas flow communication with said further rinse compartment to receive a flow of gas therefrom, a further blower arranged in said further duct to draw a flow of gas therethrough, said further duct having a discharge outlet arranged to exhaust said flow of gas from said further blower, a further body of porous material interposed in said further duct for passage of said flow of gas therethrough and providing an enlarged surface area for condensation of moisture thereon, further means for spraying water onto said further body to aid in condensing moisture thereon, and further sump means constructed and arranged for collecting condensed moisture draining from said further body.

4. A system as recited in claim 1, in which said second spraying means are arranged between said body and said discharge outlet to spray streams of water against said body in opposite direction to the flow of gas through said duct.

5. A system as recited in claim 1, together with baffle means and sump means constructed and arranged for collecting condensed moisture draining from said body and preventing reverse flow thereof through said inlet in a reverse direction to said flow of gas.

6. A system as recited in claim 1, in which said duct forms a gas flow passage extending with a vertical component of direction upwardly from said inlet to said outlet.

7. A system as recited in claim 6, together with baffle means arranged within said duct beneath said body and above said inlet to prevent flow of condensed moisture through said inlet in a reverse direction to said flow of gas.

8. A system as recited in claim 7, together with sump means arranged within said duct beneath said baffle means to collect condensed moisture draining from said body onto said batfle means.

9. A system as recited in claim 6, in which said second spraying means are arranged above said porous body in said duct to direct streams of water downwardly against said porous body.

10. A system as recited in claim 1, together with a further body of porous materiai arranged in said duct in serial gas flow relation to said first-mentioned body and spaced therefrom in the direction of gas flow.

11. A system as recited in claim 1, in which said porous body comprises expanded polyurethane foam.

body extends over substantially the entire cross-sectional area of said duct. 

1. A dishwashing machine comprising: tunnel means forming at least one rinse compartment; first means for spraying hot steam-generating water into said rinse compartment; a collection tank arranged beneath and opening into said rinse compartment to collect water draining therefrom; a steam collection system comprising a duct connected in gas flow communication with said rinse compartment to receive a flow of gas therefrom, a blower arranged in said duct to draw a flow of gas therethrough, said duct having a discharge outlet arranged to exhaust said flow of gas from said blower, a body of porous material interposed in said duct for passage of said flow of gas therethrough and providing an enlarged surface area for condensation of moisture thereon, second means for spraying water onto said body to aid in condensing moisture thereon, and sump means constructed and arranged for collecting condensed moisture draining from said body, said sump means being connected to discharge collected moisture into said rinse compartment.
 2. A dishwashing machine as recited in claim 1, said tunnel means being subdivided to form a further rinse compartment, together with third means for spraying water into said further rinse compartment, said third spraying means being connected to draw a supply of water from said collection tank associated with said first-mentioned rinse compartment.
 3. A dishwashing machine as recited in claim 2, together with a further steam collection system comprising a further duct connected in gas flow communication with said further rinse compartment to receive a flow of gas therefrom, a further blower arranged in said further duct to draw a flow of gas therethrough, said further duct having a discharge outlet arranged to exhaust said flow of gas from said further blower, a further body of porous material interposed in said further duct for passage of said flow of gas therethrough and providing an enlarged surface area for condensation of moisture thereon, further means for spraying water onto said further body to aid in condensing moisture thereon, and further sump means constructed and arranged for collecting condensed moisture draining from said further body.
 4. A system as recited in claim 1, in which said second spraying means are arranged between said body and said discharge outlet to spray streams of water against said body in opposite direction to the flow of gas through said duct.
 5. A system as recited in claim 1, together with baffle means and sump means constructed and arranged for collecting condensed moisture draining from said body and preventing reverse flow thereof through said inlet in a reverse direction to said flow of gas.
 6. A system as recited in claim 1, in which said duct forms a gas flow passage extending with a vertical component of direction upwardly from said inlet to said outlet.
 7. A system as recited in claim 6, together with baffle means arranged within said duct beneath said body and above said inlet to prevent flow of condensed moisture through said inlet in a reverse direction to said flow of gas.
 8. A system as recited in claim 7, together with sump means arranged within said duct beneath said baffle means to collect condensed moisture draining from said body onto said baffle means.
 9. A system as recited in claim 6, in which said second spraying means are arranged above said porous body in said duct to direct streams of water downwardly against said porous body.
 10. A system as recited in claim 1, together with a further body of porous material arranged in said duct in serial gas flow relation to said first-mentioned body and spaced therefrom in the direction of gas flow.
 11. A system as recited in claim 1, in which said porous body comprises expanded polyurethane foam.
 12. A system as recited in claim 11, in which said porous body is coated with polyvinyl chloride.
 13. A system as recited in claim 1, in which said porous body extends over substantially the entire cross-sectional area of said duct. 